天然橡胶/羧甲基壳聚糖抗菌复合材料的制备与性能研究

文章采用胶乳共混法制备得到了天然橡胶／羧甲基壳聚糖抗菌复合材料,并研究了材料的结构与性能。结果表明,羧甲基壳聚糖加入天然橡胶后,红外谱图上1700cm^-1。附近的吸收蜂强度发生了变化,材料的热氧化稳定忡增强,并获得了抗菌的性能,综合文章所得结果,羧甲基壳聚糖的加入量应小于4%较适宜。     

Layer-by-Layer Engineered Superparamagnetic Polyelectrolyte Hybrid Hollow Microspheres With High Magnetic Content as Drug Delivery System

Polyelectrolyte hybrid hollow microspheres with sandwich structure of about 450 nm have been accomplished by layer-by-layer self-assembling of two modified ferroferric oxide nanoparticles, lysine modified ferroferric oxide nanoparticles (Fe₃O₄-LYs) and citrate modified ferroferric oxide nanoparticles (Fe₃O₄-CA), as the main assembling materials via electrostatic interaction for the first time. They are superparamagnetic with saturation magnetization of 45.69 emu/g, revealing their high magnetic content of 70%. As drug delivery system, they also exhibited pH-stimuli responsive controlled release of an anticancer drug doxorubicin, following the Fickian diffusion model. Their unique structure and high magnetic content make them good candidate for targeted delivery.     

平行磁场作用下电沉积Co-Ni-Mn-P磁性薄膜

在平行磁场作用下电沉积Co-Ni-Mn-P磁性薄膜。研究了平行磁场对电沉积过程及薄膜性能的影响。研究发现:施加平行磁场,有利于提高离子的传质速率,从而提高沉积效率。平行磁场作用下电沉积制备的Co-Ni-Mn-P磁性薄膜呈现出"枝晶状"结构,矫顽力和比饱和磁化强度更高。     

沥滤对天然胶乳胶膜性能的影响

沥滤是天然胶乳浸渍制品一种非常有用且重要的工艺。沥滤可降低胶膜中可溶性物质的含量，改善胶膜的物理性能，降低胶膜中蛋白质含量和亚硝胺含量，从而提高制品的质量。     

磁性液体在外施磁场下的方向性弱絮凝行为

磁性液体是一种高分子稳定胶体,实验观察发现磁性液体在外施磁场作用下,磁性颗粒沿着外磁场方向形成一定有序排列的球链簇,却又不是絮凝使胶体系统失稳,显示出与其它胶体系统的不同之处。在一般胶体系统中弱絮凝行为表现不明显,不引起重视,通过计算分析发现磁性液体在外加磁场下弱絮凝行为表现却异常明显,而且弱絮凝行为存在着方向性,又不使胶体系统失稳,与实验和实际应用相符。从而揭示了磁性液体在外施磁场作用下各向异性的机理,并且很好地解释了光波在在外施磁场作用下的磁性液体中会产生光的双折射效应等现象。     

Reinforcement of natural rubber latex film by ultrafine calcium carbonate

Using ultrafine calcium carbonate to reinforce natural rubber latex film, the effect of its content on latex properties such as surface tension, viscosity, mechanical stability, and heat stability and the physical properties of latex film before and after aging such as tear strength, modulus, and tensile strength were investigated. The results showed that the surface tension of natural rubber latex reinforced by ultrafine calcium carbonate only changed slightly; when the content of calcium carbonate was less than 20%, the change of viscosity was not obvious, but when the content was greater than 20%, the viscosity significantly lowered. Ultrafine calcium carbonate could effectively improve the tear strength, tensile strength, and modulus of the natural rubber latex film. The modulus increased with the increment of the calcium carbonate. When the content of calcium carbonate was less than 15%, the tear strength and tensile strength increased with the increments of calcium carbonate, but when the content was greater than 15%, the above‐mentioned properties decreased with the increment of calcium carbonate. By comprehensive consideration, the best reinforcing effect was obtained at a content of 15% ultrafine calcium carbonate. The particle diameters of calcium carbonate and their distribution in the calcium carbonate emulsion and in the rubber film were analyzed with SEM and a laser particle size tester, which showed that the distribution of calcium carbonate in the latex film was even and that it could effectively reinforce natural rubber latex film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 982–985, 2003     

新型“胶乳法”氯化天然橡胶的研制

采用新型的"胶乳法"工艺制备氯化天然橡胶(CNR),不仅相对于传统的"溶液法"具有污染少、工艺简单、投资小、成本低等突出优点,而且解决了原"胶乳法"氯化过程橡胶分子交联严重的问题,是CNR的发展方向。介绍了该方法的反应机理、工艺流程、反应历程以及影响氯化反应的因素。研究结果表明:对现行工艺下低浓度胶乳法的氯化反应,可采用经验式预测不同相对反应时间的含氯量。根据氯含量随相对时间的变化规律,可以把反应过程分为2个阶段:高速期和低速期。在CNR氯化反应的第2阶段,反应温度的升高有利于氯含量提高,但温度过高,能量耗费过大,加上要考虑到反应的宏观动力学等因素,CNR氯化的第2阶段反应温度以343.15~353.15 K为宜。第2阶段表面活性剂平平加O的质量分数大于3%,天然胶乳的质量分数小于1%时,引发剂质量分数以0.5%~1%为宜。     

高级胶清与新鲜胶乳并用制备复合橡胶的研究

胶清经中空纤维柱过滤浓缩后,与木瓜蛋白酶反应制备高级胶清,将高级胶清与新鲜胶乳按一定干基质量比混合、共凝制备复合橡胶,研究高级胶清与新鲜胶乳并用比对复合橡胶性能的影响。结果表明:当高级胶清用量为10~40份时,复合橡胶的理化性质可达到国产5#标准胶的要求;高级胶清能促进复合橡胶的硫化并提高其物理性能。     

蒸发浓缩胶乳基本物性研究

研究了通过采用真空旋转蒸发法制备的浓缩天然胶乳（蒸浓胶乳）的机械稳定性、化学稳定性能和抗老化性能等,并与离心浓缩胶乳的有关性能进行了对照。实验结果表明,与离心浓缩胶乳相比,蒸浓胶乳机械稳定性、化学稳定性能和抗老化性能等均有所提高。     

过氧化物预硫化与硫黄硫化制备的医用天然胶乳制品热氧稳定性的差异

用TG-DTG方法研究动态空气状态下过氧化物预硫化天然胶乳(PPVL)制品试样和硫黄硫化天然胶乳制品试样的热氧降解。结果表明，PPVL试样和硫黄硫化体系试样的热氧降解反应为二步反应，前者的热氧降解起始温度To，DTG主降解峰温度L，终止温度T1均明显低于后者，反应活化能也明显低于后者；在较低温度下，两者均出现增重过程，前者比后者较明显，是后者的4．7倍；DTA曲线显示，前者出现的放热效应初始温度比后者提前。     

磁场环境中电化学制备聚苯胺膜的性能研究

文章采用循环伏安法,在磁场环境中探讨了不同的磁场方向,磁场强度、镀膜电压、镀膜圈数等因素对聚苯胺（PANI）膜电化学性能的影响,并对PANI膜进行了电化学性能测试。结果表明,在磁场环境中,采用循环伏安法制备PANI膜的较优化工艺条件是：磁场方向与电场方向瓦棚垂直,磁场强度为0．4T,镀膜电压的范围是．0．2-0．9V,镀膜圈数为40圈。     

木质素用量对乳液共沉天然橡胶性能的影响

采用共沉方法制备天然橡胶/木质素复合材料,研究了复合材料和炭黑胶料的性能以及木质素用量对天然橡胶性能的影响。结果表明,加有木质素的胶料,随着木质素用量的增加,复合材料的门尼粘度逐渐上升,炭黑胶料的最低转矩(ML)增大,最高转矩(MH)下降,正硫化时间(tc90)延长,焦烧时间(ts1)缩短,炭黑分散性变差,胶料的加工安全性、耐磨性及耐老化性变差,硫化胶的定伸应力降低。当木质素用量在20份以内时,硫化胶的拉伸强度和撕裂强度提高。     

稳恒磁场下CuCo颗粒膜电沉积制备与巨磁电阻效应

在稳恒磁场下电沉积制备了CuCo功能膜材料. 用SEM和XRD对镀层组分、微观结构进行观察和分析,并测量了膜层的巨磁电阻效应. 颗粒膜的组成随磁场强度变化而改变,0.6~0.8 T下沉积的膜层中Co含量较高,更强磁场反而抑制了Co的沉积. 施加磁场能使膜层晶粒更加致密,0.6 T磁场下制备的膜层晶粒较小,并使膜层(111)晶面择优取向增强. 磁阻测试表明,0.6 T磁场下制备的CuCo颗粒膜经真空退火处理后,巨磁电阻较无磁场下提高约25%.     

Preparation and Properties of Natural Rubber/Palygorskite Composites by Co-Coagulating Rubber Latex and Clay Aqueous Suspension

Natural rubber (NR)/Palygorskite composites were prepared by co-coagulating rubber latex and clay aqueous suspension. Org-palygorskite was attained by using cetyltrimethylammonium bromide (CTAB) and the four factors influencing the average diameter of palygorskite were discussed. Four optimal conditions of preparing minimum average diameter were determined which included the concentration of palygorskite, the concentration of sodium polyacrylate, ultrasonic time and ultrasonic power. Mechanical properties suggested that composites using modified palygorskite which were dispersed by ultrasonic wave were the best, the tensile strength, tear strength, 300% modulus and shall hardness increased by 77.14%, 118.18%, 242.86% and 65.2%, respectively. Modified palygorskite was shown by FTIR spectrogram and observed by ESEM. Modified palygorskite dispersed by ultrasonic wave were dispersed into the rubble uniformly, some stick particles inserted into the rubber and it is difficult to find stick shape, and there were 20% particles belonging to nanomaterials and 80% micromaterials.     

热裂解气相色谱法测定天然胶乳中的干胶含量

研究热裂解气相色谱法测定天然胶乳中的干胶含量。试验结果表明,干胶含量与裂解主要产物峰面积呈现良好的线性关系,采用标准曲线法测定天然胶乳中的干胶含量,重复测定的相对标准偏差为0.14%,与国标法的平均相对误差为1.51%,定量分析结果准确,操作简便。     

磁场下电沉积制备Co-Pt-P磁性薄膜

在磁场下电沉积制备Co-Pt-P磁性薄膜。研究了电流、温度、磁场强度对薄膜性能的影响。结果表明:磁场对镀层的成分、微观结构及磁性能有一定程度的影响。     

降解天然橡胶胶乳的接枝共聚研究

研究了不同降解程度的天然橡胶胶乳与丙烯酸丁酯 ( BA)的接枝反应及反应条件对接枝率的影响。发现随着降解时间增加 ,降解橡胶的粘均相对分子质量降低不是直线下降 ,而是有一个明显的突跃 ,降解胶乳共聚反应活性并未降低 ,且共聚物中 BA聚合链段与橡胶链段的相对比例 (质量比 )明显增加     

Improvement of Physico-Mechanical Properties of Radiation-Vulcanised Natural Rubber Latex Films by Adding Urea

The role of urea as an additive on the physico-mechanical properties of radiation vulcanised natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of urea with the concentration range 0–1.0 phr (parts per hundred rubber) and irradiated with various radiation doses (0–20 kGy). The concentration of urea and radiation doses were optimised and found to be 0.5 phr urea and 12 kGy radiation dose. Tensile strength, tear strength and cross-linking density of the rubber films increased with increasing the concentration of urea as well as radiation doses. The tensile and tear strengths of the films enhanced by 39 and 41%, respectively, at the optimum conditions. Elongation at break, permanent set and swelling ratio of the films decreased with increasing urea concentration and radiation doses until they attained approximately constant values.     

使用核磁共振交联密度仪测试不同方法凝固天然橡胶的交联密度和性能的关系

用核磁共振(NMR)法测定不同方法凝固天然橡胶的交联密度,研究其与性能之间的关系。结果表明,硫化胶的交联密度不仅影响其核磁共振的横向弛豫时间(T1),而且影响其纵向弛豫时间(T2)。随着交联密度大,硫化胶的核磁共振弛豫时间缩短。另外,微生物凝固天然橡胶硫化胶的交联密度、正硫化时刻扭矩和拉伸强度均大于酸凝固天然橡胶硫化胶的。     

Diffusive Capture of Magnetic Particles by an Assemblage of Random Cylindrical Collectors

Abstract

We develop an effective medium model describing the capture of ultra-fine magnetic particles (diameter much less than 1 µm) by an assemblage of parallel magnetic cylinders, randomly distributed in static fluid. The continuity equation describing the dynamics of concentration is solved numerically to obtain the concentration in various regions around the collector. The concentration contours are generated and the saturation, accumulation, and depletion regions are indicated. The effect of varying collector packing fractions appears significantly in regions close to the outer boundary of the representative cell where the build-up features of ultra-fine particles near the collector surface are similar for packing fractions in range 5–10%.